British attempts to weld pro-government fighters in Sierra Leone into an effective force were set back yesterday when the army and militia turned on each other during a rebel assault on Masiaka, a town about 40 miles east of the capital.
Elsewhere the army and UN forces pushed back the Revolutionary United Front (RUF) as the British laid the ground for an assault on the diamond fields, which fund the rebels' war.
The UN said last night that 18 of the nearly 500 peacekeepers being held hostage by the RUF had been released near the Liberian border, including the only known British detainee. But it was not clear if the move heralded a mass release of the others.
The chief of Britain's defence staff, Gen Sir Charles Guthrie, arrived in Freetown yesterday to reiterate the British government's line that its troops were not there to engage in combat against the RUF.
"It's absolutely clear why the British troops are here. They are here to evacuate our people, British passport holders," he said. "We are not part of the UN [force]. We do not intend to be part of the UN."
But by Saturday there were so few Britons remaining in Freetown who wished to be evacuated that the only people to be flown to Senegal were a group of Senegalese.
Sierra Leonean forces held the town of Masiaka yesterday even though members of the army turned on their supposed allies, the Kamajor militia, during a rebel assault.
The battle was important because Masiaka was being reinforced as a launch pad for attacks deeper into RUF territory.
The Sierra Leone government meanwhile continued to arrest RUF officials it accuses of plotting a coup accidentally foiled by the rebels themselves when they fired on an unarmed protest march a week ago, killing 19 people.
More than 30 senior RUF leaders have been picked up at their homes and in hotels.
At the weekend the Justice Minister, Mr Solomon Berewa, accused the RUF leader, Mr Foday Sankoh, of planning a "very violent coup" in which leading government officials and supporters were to be executed.
Mr Berewa said that the rebels had taken almost 500 peacekeepers hostage in order to paralyse the UN before the planned coup.
Mr Sankoh's whereabouts remain a mystery. He has not been seen publicly for a week. His disappearance has prompted speculation in the Freetown press that he is dead. Some papers have carried vivid descriptions of how he was strangled or bludgeoned to death by Nigerian soldiers.
The World Food Programme said it was concerned about the fate of at least 65,000 displaced people trapped in rebel-held areas, who were reliant on food aid. Its spokeswoman, Ms Aya Schneerson, said there had been no deliveries to camps in parts of the north and centre of the country since the crisis erupted nearly two weeks ago.
"Our concerns are for the ones we can't reach and the fact that it's getting close to the planting season. If you have a crisis when the planting season starts, that's not good in the long run," she said.
Richard Norton-Taylor adds from London: The arrival of a naval amphibious task force off the west African coast yesterday pointed to further British military involvement in Sierra Leone, despite adamant ministerial denials of "mission creep".
The British Foreign Secretary, Mr Robin Cook, who said that the expertise shown by the British troops in Sierra Leone had "reinforced respect for Britain around the world", insisted that they would not get involved in combat duties with the UN.
He said on BBC TV: "We expect this to be over in a month. We want it to be over in a month, and we want to keep that deadline there as pressure on the UN to get their people there in a month. We don't want that timetable to slip . . . What we cannot do is contribute combat troops. That is not going to change."
Sierra Leone's rebel movement has freed 139 of more than 500 UN personnel held captive into Liberian custody, Liberia's president, Mr Charles Taylor, said. He said 15 of the freed captives had been flown by helicopter to Liberia's capital, Monrovia, while the remaining 124 were waiting to be evacuated from the Liberian border town of Foya. There was no immediate UN confirmation of the report.